Thank you for a very good question and welcome to our community. I would guess that the life of the Never Wet will depend on the conditions it is exposed to.

I live out on the West coast and I just sprayed the fabric cover to my iron tub fire pit with Never Wet. I am very happy with the results but how long will this last? We will have to wait to find out. Since my cover does not get a lot of activity, I would think that the water proofing will last longer than that of the bottom of a lawn mower. We will have to wait and see.

I applied the Never Wet to my cover on June 18, 2013. I will keep you posted on how is holds up. Before I applied the Never Wet, the water just soaked into my cover.

After I applied the Never Wet, the water just rolled off the cover. I was impressed.

Be sure to take a video of your Never Wet project and share it with us in our Project Library under "I Did This".

I applied the Rust-Oleum Never Wet to the cover of my fire pit and will the results were very impressive. I will monitor my fire pit cover and let you know how long the NeverWet application lasts.

I live out here on the West Coast and we do not get much rain in the summer. We do get plenty of sun and that may be an issue for the Rust-Oleum NeverWet product. I will let you know if any thing developes. As with any type of coating, Mother Nature has a way of wearing on it.

On a metal and tile garden table, and also on bricks around my house, it's still working great after 3-4 weeks.

On cast aluminum parts, it worked great for a while, but after I washed the parts with detergent the effectiveness of the costing diminished noticeably. So, as noted in the product usage information, detergents seem to degrade it.

On a baseball cap, results are in between the above examples. Coating is holding up pretty well, but where it's become worn from use, like where I grab the brim putting the hat on, it does not shed water very well anymore. I suspect a combination of coating wearing off, and skin oil from my hands, is interfering with the performance.

So, as Rick suggested above, performance varies with the application. It looks to me like hard surfaces which are not subject to cleaning with detergents are an ideal application that results in optimal life of the performance. Abrasion and chemical contamination appear to diminish the performance.

Twittig,

Since it's not possible to definitively quantify such factors, it would be impossible for Neverwet to 'provide a definitive answer' to this question. But if you experiment with various test applications, like I did, you will get a better idea what to expect. It's neat stuff for sure, but you need to understand it's limitations to take best advantage of it's potential.